Warewash machine with controlled retention of liquid in suspension

ABSTRACT

A warewash machine includes at least one collection tank for collecting wash liquid that is recirculated by a pump and sprayed for cleaning wares within a spray zone of the machine. An overflow path leads from the collection tank, and an automated valve controls flow along the overflow path. A controller is configured to control an open/closed state of the automated valve based at least in part upon status of pump operation

TECHNICAL FIELD

This application relates generally to commercial warewash machines and, more specifically, to commercial warewash machines that utilize recirculating sprays of liquid in one or more wash zones.

BACKGROUND

Commercial warewashers commonly include a housing area which defines spray zones in the nature of washing and rinsing zones for dishes, pots pans and other wares. In certain zones, wash liquid (e.g., water or water and detergent) is typically pumped from a tank through a pump intake, delivered to the wares via a spraying operation from multiple nozzles located in one or more spray arms and collected in the tank for recirculation through the spray system. One or more of the spray zones may also include an overflow to drain (e.g., which may be a standpipe type overflow or may be an overflow through the sidewall of the tank). As fresh water is added into the machine (e.g., through the rinse arms) dirtier water overflows to drain.

The liquid in the spray recirculation line, pump and in the actual sprays of a spray zone can be referred to as liquids in suspension because at any given time they do not contribute to the volume of liquid in the collection tank of the zone.

In the current operation of known warewash machines, especially the conveyance-type machines (e.g., rack conveyance or flight-type conveyance through the spray zones), substantial loss of water, chemicals and/or energy occurs anytime a tank recirculation pump shuts down. By way of example, such shut down may occur as a result of any of a dish limit activation after some time, running the machine in idle mode while maintaining tank temps, or an operator opening the machine door for some reason, which automatically interrupts washing and stop the recirculation pumps. These intermittent stops results in loss of energy, chemical and water as results of the suspended hot solution overflowing to drain. Specifically, the liquid in suspension, which may, for example be between six and ten gallons for a given spray zone, falls down into the collection tank, causing the tank level to rise above an overflow level, such that a large volume (e.g., six to ten gallons) of liquid moves to drain. In a machine with multiple spray zones, the liquid volume lost to drain is even more (e.g., in a machine with three recirculating spray zones 18 to 30 gallons may be lost by overflow to drain in such cases).

Upon restarting wash operations after such a stop, fresh, generally cold water from the rinse and/or tank fill lines replenishes the lost fluid. In addition, chemicals (especially detergents) are added to achieve to the correct detergent concentration for washing. The addition of the fresh cold water to make up for the lost water drops the overall wash tank temperatures, which requires time and energy to heat the tank contents to acceptable tank liquid temperatures.

Moreover, in the current machine in which the hot wash solution falling out of suspension goes to drain makes the machine prone to cavitation, foaming and possible pump problems, upon restarting the machine for the next wash cycle, because part of the tank fluids need to be suspended while the rinse and fill are on to replenish the suspended fluids. This often takes some time and depends on the type of machine.

It would be desirable to provide a machine that is configured to avoid unnecessary losses such as those described above.

SUMMARY

In one aspect, a warewash machine allows liquid in suspension to be collected/retained within a collection tank of the machine without overflowing to drain so that the liquid can be re-used.

In another aspect, a method is provided for operating a warewash machine that includes at least one collection tank for collecting wash liquid that is recirculated by a pump and sprayed for cleaning wares within a spray zone of the machine. The method involves: utilizing an automated valve to control overflow draining from the collection tank; while the pump is operating to recirculate wash liquid, maintaining the automated valve in an open condition to allow liquid to overflow from the tank as the water level in the tank rises due to addition of water by dilution or capture of final rinse liquid; and automatically closing the automated valve in conjunction with stopping operation of the pump so that at least some liquid in suspension falls into the collection tank and liquid level in the collection tank rises above a normal overflow level of the collection tank.

In another aspect, a warewash machine includes at least one collection tank for collecting wash liquid that is recirculated by a pump and sprayed for cleaning wares within a spray zone of the machine. An overflow path leads from the collection tank, and an automated valve controls flow along the overflow path. A controller is configured to control an open/closed state of the automated valve based at least in part upon status of pump operation.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of one embodiment of a warewash machine;

FIG. 2 is a schematic depiction of another embodiment of a warewash machine; and

FIG. 3 is a schematic depiction of another embodiment of a warewash machine.

DETAILED DESCRIPTION

A warewash machine is configured to reduce losses upon machine or recirculation pump shutdown. In particular, the machine is configured to capture some or all of the hot wash solution that falls out of suspension during a stop, preventing it from going to drain, so that it can be reused in the next wash cycle. An automatic valve can be used for this purpose, and will significantly improve the warewash machine operational sequence to save energy and material(s) (e.g., chemicals and water).

Referring to FIG. 1, a schematic end elevation of an exemplary conveyance-type machine 10 is shown. The machine includes a housing 12 defining a tunnel through which the wares are delivered by a conveyance mechanism 14 (ware movement would be in or out of the page in this end view). An exemplary spray zone 20 of the machine includes one or more upper spray arms 22 and/or one or more lower spray arms 24, it being recognized that in some cases a spray zone may, in addition or as an alternative, include one or more side spray arms (not shown) as well. A wash liquid recirculation system includes a liquid collection tank 26, recirculation line 28 back to the spray arms 22, 24 and pump 30 for moving the wash liquid along the path. An overflow path 32 to drain is also provided from the tank, and an automated valve 34 is located along the path 32. Path 32 may be direct to drain, or may be a path that passes through one or more additional tanks of other spray zones before flowing to drain.

A machine controller 100 is connected for controlling operation of both the pump 30 and valve 34. As used herein, the term controller is also intended to broadly encompass any circuit (e.g., solid state, application specific integrated circuit (ASIC), an electronic circuit, a combinational logic circuit, a field programmable gate array (FPGA)), processor (e.g., shared, dedicated, or group—including hardware or software that executes code) or other component, or a combination of some or all of the above, that carries out the control functions of the machine or the control functions of any component thereof.

During machine operation, the liquid in the tank 26 does not exceed the level indicated by dashed line 36 due to the overflow drain path 32, because the automated valve 34 is maintained in an open condition while the pump 30 is operating to provide the recirculating spray flow. When the pump 30 is shut down for some reason, the controller 100 effects closure of the valve 34 so that the overflow path 32 is effectively closed, allowing the liquid in suspension to be captured in the tank, in which case the liquid level rises to the level indicated by dashed line 38. The difference between the liquid levels 38 and 36 represents the amount of liquid savings achieved by automatic closure of the valve 34, which in turn results in savings of both energy and detergent that would have been needed if the liquid had been permitted to overflow to drain. The overall savings on water, energy and chemicals can be significant, particularly for machine installations in which temporary shut downs occur more frequently.

With respect to closure of the automated valve 34, in some implementations it may be desirable to close the valve 34 substantially simultaneously with the shutdown of the pump 30 (e.g., just before, at the same time as, or just after), resulting in capture and retention of substantially all of the liquid in suspension so that it is not lost to drain. In other implementations, it may be desirable allow some of the liquid in suspension to overflow before shutting down the valve. For example, the valve 34 could be maintained open for a set time period after shut down of the pump 30 (e.g., valve 34 maintained open for between 1-5 seconds (such as 1-2 seconds) after pump shutdown), so that only a portion (e.g., at least 50%, such as between 50% and 90%, such as between 60% and 80%) of the volume of liquid in suspension is precluded from following the overflow path. It is recognized that the exact timing of valve closure, whether substantially simultaneous or after some time period, could be a settable feature of the machine. For example, the controller 100 could include a user interface 102 that that enables an end user, or on some cases only maintenance or service personnel, to adjust the timing of valve closure relative to the timing of pump shutdown, thereby enabling the portion of the volume of liquid in suspension that will be prevented from overflowing to drain to be set at virtually any percentage (e.g., between 5% and 100%).

Upon restart of the machine for operation, specifically when operation of the pump 30 is restarted, the controller 100 again effects opening of the valve 34 to permit normal overflow operations as desired. Although closure of the valve 34 may in some cases be substantially simultaneous with the restart of the pump 30, it is recognized that it will typically take some amount of time for the previously captured liquid (represented by the difference in liquid levels 38 and 36) to again be put into suspension. Accordingly, closure of the valve 34 may more commonly be effected by the controller at some time after restart of the pump 30 (e.g., after a set or settable time period, or after detecting, such as by way of a level sensor 40, that a liquid level in the tank 26 has dropped to a certain level).

As described above, a typical conveyance-type warewash machine include multiple spray zones. In this regard, reference is made to the schematic side elevation of the exemplary warewash machine 110 of FIG. 2, which includes recirculating spray zones 112, 114, 116, 118 and 120, each zone having respective tanks 122, 124, 126, 128 and 130, respective pumps 132, 134, 136, 138 and 140 and respective spray arm(s) 142, 144, 146, 148 and 150. Ware travel through the machine is from left to right as indicated by arrows 152. Zone 112 represents an automated soil removal zone, where the largest soils are removed from incoming wares. Zone 114 represents a prewash zone, zone 116 represents a main wash zone, zone 118 represents a power rinse zone (aka post wash zone) and zone 120 represents a dual rinse zone (aka secondary rinse zone). A final rinse zone 154 is also provided, and sprays fresh hot rinse liquid as may be delivered by pump 156 from booster heater 158. One or more drying zones (not shown) could also be provided.

Generally, all pumps are turned ON/OFF simultaneously, except the fresh hot rinse liquid pump 156 which turns ON when wares are in the final rinse zone 154 and off when no ware is present in the final rinse zone 154. During cleaning operations with the pumps on, fresh rinse liquid is delivered into the machine in zone 154 and the used rinse liquid is diverted to the tank 130 of the dual rinse zone 120. Overflow paths 160, 162, 164 and 166 are provided between the tanks, resulting in a reverse cascade overflow path from tank 130 to tank 122. Tank 122 includes an overflow path 168 to drain through a master manual valve MV and an automated valve AV connected in parallel. Each tank also includes a respective manual drain valve M1-M5 that can be used to fully drain the tank for machine cleaning. An exemplary operational sequence for machine 110 is described below.

When the machine is in operation the master manual drain valve MV and the individual manual drain valves M1, M2, M3, M4 and M5 are closed, while the automatic valve AV is opened. The automatic master drain valve AV is maintained in an open condition so long as the final rinse pump 156 is operating to allow for draining of the used final rinse water, which cascades sequentially through the various tanks 130, 128, 126, 124 and 122 to sweeten or dilute the wash solutions in each tank as the liquid level in each tank rises due to the incoming fresh final rinse water. The cascade finally goes to drain via overflow line 168 from tank 122. While the spray zone pumps 132-140 are operating, but when the final rinse pump 156 is not operating (i.e., no wares in the final rinse zone 154), the automated drain valve AV can be closed if desired because new water is not being added to the machine. However, it may more typically be maintained open. The automatic master drain valve AV closes when the wash pump 136 shuts down. Note that the wash pump 136 and the other tank pumps 132, 134, 138 and 140 typically all shutdown simultaneously.

When the wash pump 136 stops, the automatic drain valve AV closes to capture suspended hot wash solution from going to drain. As used herein, closing the valve “when operation of the pump is stopped” could be achieved by closing the valve just before, simultaneous with or just after the wash pump is turned off. Moreover, a set delay in closure of the automated valve AV could also be used as described above. The water levels in all of the tanks rise above the normal overflow levels because both the automated drain valve AV and the master manual valve MV are closed, thereby capturing and retaining a large volume of the liquid in suspension (e.g., in this case potentially between 30 gallons and 50 gallons, assuming between 6 and 10 gallons in suspension in each zone 122, 124, 126, 128 and 130). Upon initiating the next wash cycle (e.g., restarting the machine pumps), the captured wash solution is reused. Operation of the pump(s) again moves some of the liquid into suspension and the water levels in the tanks fall back below the overflow levels. Thus, at restart the required fresh water add is significantly reduced, which likewise reduces the amount of chemical add required as well as the amount of energy needed to maintain the tank liquid at required temperature.

The automated drain valve AV is automatically opened as part of the machine restart. In one example, the valve may be opened at the same time the pumps start. In another example, as previously noted, the valve may be opened a specified time period after the pumps start to provide some time for liquid to go into suspension, or after liquid level in the tank has dropped a specified amount due to resuspension of liquid.

During a machine start-up from empty, the valve AV would be maintained closed to allow all tanks to fill.

Draining the tank(s) for refill after dumping or at shutdown will typically involve opening all the manual valves including main valve MV, as well the automatic valve AV for quicker draining.

Referring now to FIG. 3, a schematic side elevation of another exemplary machine 210 is shown, which is similar in configuration to the machine 110 is shown. However, in the case of machine 210 the automated valve AV is located in series with the master manual valve MV, rather than in parallel. Thus, in this configuration, during normal operation of the machine the master valve MV would be maintained in the open condition to allow for overflow draining from the machine. Otherwise, operation of the machine 210 is the same as that described above for machine 110.

The above machines and processes can save energy, chemicals and water. Initial onset of pump cavitation, foaming can be reduced as well as protection of machine parts. Reuse of captured solution in suspension for subsequent operation reduces colder water refills required to replenish any lost wash solution, chemical make-up required and time for the machine to get to temperature suitable for wash operations.

It is to be clearly understood that the above description is intended by way of illustration and example only, is not intended to be taken by way of limitation, and that other changes and modifications are possible. 

What is claimed is:
 1. A method of operating a warewash machine that includes at least one collection tank for collecting wash liquid that is recirculated by a pump and sprayed for cleaning wares within a spray zone of the machine, the method comprising: utilizing an automated valve to control overflow draining from the collection tank; while the pump is operating to recirculate wash liquid, maintaining the automated valve in an open condition at least when fresh liquid is also being added to the machine to allow liquid to overflow from the tank as the water level in the tank rises due to addition of water by dilution or capture of final rinse liquid; automatically closing the automated valve in conjunction with stopping operation of the pump so that at least some liquid in suspension falls into the collection tank and liquid level in the collection tank rises above a normal overflow level of the collection tank.
 2. The method of claim 1 wherein the automated valve is closed substantially simultaneously with stopping operation of the pump, resulting in capture and retention of substantially all of liquid in suspension so that it is not lost to overflow.
 3. The method of claim 1 wherein the automated valve is closed a set time period after stopping operation of the pump, so that only a portion liquid in suspension is precluded from following the overflow path.
 4. The method of claim 1 wherein the automated valve is located either (i) in parallel with a manual valve of a drain line or (ii) in series with a manual valve of a drain line.
 5. The method of claim 1 wherein in conjunction with restart of operation of the pump, the automated valve is automatically opened.
 6. The method of claim 5 wherein the automated valve is opened substantially simultaneous with restart of operation of the pump.
 7. The method of claim 5 wherein the automated valve is opened after restart of operation of the pump.
 8. The method of claim 5 wherein the automated valve is either (i) opened a set time period after restart of operation of the pump or (ii) opened when liquid level in the collection tank falls to a set level due to resuspension of some liquid.
 9. The method of claim 1 wherein the warewash machine includes multiple spray zones with respective collection tanks, a cascading sequential overflow from tank to tank and a final overflow path to drain from an initial spray zone of the machine, the automated valve controls flow along the final overflow path to drain, and at least twenty gallons of liquid in suspension in the machine is retained within the machine as a result of closing of the automated valve.
 10. The method of claim 9 wherein at least thirty gallons of liquid in suspension in the machine is retained within the machine as a result of closing of the automated valve.
 11. A warewash machine, comprising: at least one collection tank for collecting wash liquid that is recirculated by a pump and sprayed for cleaning wares within a spray zone of the machine; an overflow path leading from the collection tank; an automated valve to control flow along the overflow path; and a controller configured to control an open/closed state of the automated valve based at least in part upon status of pump operation.
 12. The machine of claim 11 wherein the controller is configured to maintain the automated valve in an open state during operation of the pump for ware cleaning and at least when fresh liquid is being added to the machine, and to close the automated valve in conjunction with stopping operation of the pump.
 13. The machine of claim 12 wherein the controller is configured to close the automated valve substantially simultaneously with stopping operation of the pump, resulting in capture and retention of substantially all of liquid in suspension so that it is not lost to overflow.
 14. The machine of claim 12 wherein the controller is configured to close the automated valve a set time period after stopping operation of the pump, so that only a portion liquid in suspension is precluded from following the overflow path.
 15. The machine of claim 11 wherein the automated valve is located either (i) in parallel with a manual valve of a drain line or (ii) in series with a manual valve of a drain line.
 16. The machine of claim 11 wherein controller is configured to open the automated valve in conjunction with restart of operation of the pump.
 17. The machine of claim 16 wherein the controller is configured to open the automated valve simultaneous with restart of operation of the pump.
 18. The machine of claim 16 wherein the controller is configured to open the automated valve after restart of operation of the pump.
 19. The machine of claim 18 wherein the controller is configured to open the automated valve either (i) a set time period after restart of operation of the pump or (ii) when liquid level in the collection tank falls to a set level due to resuspension of some liquid by operation of the pump.
 20. The machine of claim 11 wherein the warewash machine includes multiple spray zones with respective collection tanks, a cascading sequential overflow from tank to tank and a final overflow path to drain from an initial spray zone of the machine, the automated valve controls flow along the final overflow path to drain, and at least twenty gallons of liquid in suspension in the machine is retained within the machine as a result of automatic closing of the automated valve. 